Dropping the Ball in a Rotating Space Settlement

Here’s a virtual space settlement “ball drop” experiment courtesy of Joe Strout. The ball starts out six meters above the deck, initially stationary with respect to the rotating settlement. Then it is dropped, much like Galileo dropping stones from the Leaning Tower of Pisa, but it results in a behavior that Galileo never saw:

The viewpoint is lined up for optimally seeing the slight pull to the left. In reality, of course, there is no pull to the left… the ball is traveling in a straight line, at a constant velocity from the moment it was released, and the settlement is rotating around it. Note that the appearance of moving toward the viewer is an illusion: the ball is not being dropped from the vertical dark pillar but from an invisible platform the same distance toward the viewer as where the ball lands.

Details for the curious: The deck here has a 224-m radius and spins at 2 RPM, simulating 1G. The white ceiling at the top of the view is about 130 m up. Those deck plates are 2 m squares, though unfortunately they don’t line up perfectly with the ball’s starting position — but if you can detect a slight bend in the plating, that does align with where the ball starts. So the ball’s apparent sideways motion is about a meter or so, over a 6 meter drop.

Note that this simulation assumes there is no air here; the ball is falling as in a vacuum. In a real settlement, of course, air would apply a force in the direction of the settlement’s spin, reducing this Coriolis effect by some amount that depends on the aerodynamics of the object.

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